(1) Field of the Invention
The present invention relates to an aqueous colored polymer. More particularly, it relates to an aqueous colored polymer having a film-forming property at normal temperature, and a process for the preparation thereof and uses thereof. More specifically, the present invention relates to an aqueous colored polymer containing a sulfonic acid group, which is dyed with a basic dye, and a process for the preparation thereof and uses thereof.
(2) Description of the Prior Art
Inorganic or organic pigments have heretofore been used for coloring aqueous polymer emulsions or aqueous polymer solutions. Furthermore, acid dyes and direct dyes have also been used in the form of aqueous solutions thereof.
Such conventional techniques, however, have various defects as described below. Namely, the coloration with pigments is restricted because the number of colors of the pigments is limited, and it is impossible to increase the color value. Moreover, the pigments are expensive. Furthermore, in order to attain the intended coloring effect in an aqueous ink or the like, it is necessary to pulverize pigments into fine particles according to various methods and disperse the resulting fine particles in water with use of a large quantity of a dispersing agent or dispersion stabilizer. Accordingly, preparation of such aqueous dispersions of pigments is very difficult. Moreover, when aqueous inks are prepared from these aqueous dispersions, sedimentation of the pigment particles occurs with the lapse of time, and thus, the storage stability of products is poor and clogging of ink nozzles is readily caused. In an extreme case, attainments of the intended effect or application to the intended use becomes impossible.
In this process for coloring an aqueous polymer with a pigment dispersion, a polymer emulsion or aqueous polymer acts as a binder for the pigment, and the polymer per se present in the emulsion or aqueous solution is not colored.
In case of the coloring method using an aqueous solution of an acid dye or direct dye as a colorant, such as an aqueous ink, since the dye per se is water-soluble, the water resistance of a colored material after drying is very poor and blurring of the color is caused by water or sweat, or the color is readily washed away. Also in this case, the polymer per se is not colored.
As means for overcoming the defects of the coloring method using a pigment dispersion, there has been proposed a process in which colored particles of an acrylonitrile polymer are used as a colorant for an aqueous polymer emulsion (see Japanese Unexamined Patent Publication No. 52-80340).
This process, however, requires a special polymerization process (for example, the polymerization is carried out at a temperature of at least 120.degree. C. under a high pressure of 5 to 50 atmospheres) for obtaining such a finely divided polymer that colored polymer particles can be used as a colorant. Moreover, since the monomer composition constituting the polymer particles is restricted, the polymer particles cannot be applied to uses where good film-forming property and flexibility are required.
As pointed out hereinbefore, it is known that a water-soluble dye can be used as an aqueous colorant, and basic dyes are excellent over other dyes in the color abundance and the color brightness. However, basic dyes are not satisfactory because of poor light fastness.